This invention relates to the fabrication of circuit arrays and, more particularly, to a technique for electrical identification of the circuit configuration formed in a multiply configurable circuit array.
A general-purpose integrated-circuit array such as a read-only memory is programmed during fabrication (by utilizing different masks) to establish therein a particular multiple-word representation specified by a user. In practice, such a general-purpose array may be made in hundreds of different variations or codes to respectively store hundreds of different representations. Keeping track of such a large number of almost visually indistinguishable but electrically different integrated-circuit chips during the manufacturing process is a burdensome and expensive task.
Hence, the need arose for some way of easily determining the code of a mask-programmed array so that the array could be tested and later sorted for marking without having to maintain records of the identity of the code during the entire manufacturing process.